Such devices are already well known and in relatively wide use in spite of their high cost. Very briefly, such a device comprises a frame supporting a magnet including means for generating a magnetic field in which the lines of force are all oriented in the same direction. These field generator means are generally constituted by a plurality of turns wound side by side to constitute a magnetic oil defining an empty space in the center thereof through which the lines of force of a uniform "main" magnetic field extend.
The device further includes, in association with the magnet, a support for supporting the body of a patient, e.g. a bed mounted on means enabling the bed to be moved through the center of the coil in a direction parallel to the lines of force of the magnetic field provided by the coil.
This generator of a static longitudinal magnetic field is associated with means for setting up other magnetic fields having gradients and capable of being oriented, for example, along three different directions in the space occupied by the volume of the portion of the body under examination for the purpose of forming an image thereof, e.g. the brain in the above-mentioned example, together with radio frequency excitation means, and means for detecting nuclear magnetic resonance signals produced by some of the atoms in the portion of the body being scanned.
It should also be specified that in some devices the excitation means and the detection means may be constituted by a common sensor portion, with merely the input means to said sensor changing with the desired function, i.e. excitation or detection. The person skilled in the art commonly refers to this type of sensor by the term "antenna".
There are various different possible structures for such antennas, generally making it possible to define a cylindrical zone suitable for being placed in the center of the magnetic coil with the axis of the cylindrical zone extending in the same direction as the above-defined main magnetic field. However, in order to be fully effective, this cylindrical zone should surround the portion of the body to be scanned, and should surround it as closely as possible.
In order to achieve the result, attempts have been made to provide special sensor structures, however none of them have given advantageous results so far, i.e. facilitating installation of the sensor in the imaging device around the portion of the patient's body to be scanned and surrounding said portion as closely as possible.
The object of the present invention is to provide a nuclear magnetic resonance imaging device, and more particularly an "antenna" element therefor of a structure enabling it to be adapted very easily to image making requirements with respect to the portion of the body to be scanned, and also fitting closely around said portion of the body and surrounding it as closely as possible, for the purpose of setting up secondary magnetic fields in different orientations relative to the main magnetic field generated by the magnet.